Motor bearing problems

R

Riccio

New member
Hi guys, I congratulate you for the forum created really something innovative and exciting for the future of automobiles. We are trying to supercharge a motorcycle engine with poor results. The issue is that being low displacement (700 cc) the flow rate is oversaturated but the pressure generated is too low due to the low rotational speeds. In the initial setup we used a 60000 rpm motor with a TD04L-13T impeller glued to the crankshaft.

The issue is the low overpressure achieved because of the low rotational speed. For this reason we purchased a TP4060-CM also with the same impeller but after several tests at 78000 rpm something went wrong and the bearing on the output side of the shaft now at axial clearance. We don't know whether to blame: the motor, the poor balance of the impeller or our assembly.
The problem is that the system needs to have decent reliability but at the same time be light (which is why we shelved the volumetric compressors).
Since due to gluing it is not possible to recover either the turbine or the motor and if we want to go up a lot of RPM e.g. above 100000 we were considering using an RPM multiplication system. This allows us to separate the two components and have an motor running at a lower speed. From Alex's videos we can see that the timing belt has non-indefferent friction since it heats up quickly.

At this point we rely on your advice to get something working.
 
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How do you fixe your impeller to the motor shaft? Because at this speed, even a 0.001" axial tolerance is not enough. This play can easily break you motor bearing.
 
I have decided to go geared.. it will mean i'll have to make a gearbox (3d print at this point) to hold gear oil...
But id rather do that because i believe it will 100% work than go pulleys and have it maybe work.. and if it works have questionable life expectancy ..

On the bearings what bearings did you use ?
Someone had previously pointed out that the bearings on the CM motors are actually not very good and in theory aren't capable of running at the high rpm that motor theoretically can and therefore should be replaced with ceramic ball ones.
 
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WB projects said:
How do you fixe your impeller to the motor shaft? Because at this speed, even a 0.001" axial tolerance is not enough. This play can easily break you motor bearing.
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Thank you for your reply. The impeller is glued to the motor shaft with structural glue. The impeller hole and motor shaft have the "same" diameter. But like you said small assembly errors and small differences in diameters result in big problem. How we could try to solve the problem? Maybe I think that high speed are the biggest challenge but with motorbikes engine it's difficult to obtain high pressure at low impeller speed.
 
MkngStffAwesome said:
I have decided to go geared.. it will mean i'll have to make a gearbox (3d print at this point) to hold gear oil...
But id rather do that because i believe it will 100% work than go pulleys and have it maybe work.. and if it works have questionable life expectancy ..

On the bearings what bearings did you use ?
Someone had previously pointed out that the bearings on the CM motors are actually not very good and in theory aren't capable of running at the high rpm that motor theoretically can and therefore should be replaced with ceramic ball ones.
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Thank you for your reply. After several test we think that the best solution is pulley. You may have the option of changing the multiplication ratio, but this involves an increase in weight and additional work. We used the stock bearings and thought we had a good product on our hands.

The goal was to get a CASTLE 2028. It seems to be more robust but necessarily requires a multiplier given the low RPMs. The question find a reliable system with low losses and that achieves very high speeds on the impeller.
 
Riccio said:
Thank you for your reply. The impeller is glued to the motor shaft with structural glue. The impeller hole and motor shaft have the "same" diameter. But like you said small assembly errors and small differences in diameters result in big problem. How we could try to solve the problem? Maybe I think that high speed are the biggest challenge but with motorbikes engine it's difficult to obtain high pressure at low impeller speed.
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If you drill your impeller yourself by hand, its probably the problem. The glue and everything is not the main problem. Maybe only for balencing purpose. But if it was me, I would use a milling machine, indicate the wheel to be at 0.000", drill it and ream it. If you use a normal press drill,I can assume that you have at least 0.005" of uncentered.
 
WB projects said:
If you drill your impeller yourself by hand, its probably the problem. The glue and everything is not the main problem. Maybe only for balencing purpose. But if it was me, I would use a milling machine, indicate the wheel to be at 0.000", drill it and ream it. If you use a normal press drill,I can assume that you have at least 0.005" of uncentered.
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The impeller already comes drilled. We cannot check the tollerance before assembly.
 
Well, that's weird. If the impeller weel goes on the motor shaft with no play, there's not suppose to have problem here. How's look the glue? Can you post a picture here to see your set up?
 
WB projects said:
Well, that's weird. If the impeller weel goes on the motor shaft with no play, there's not suppose to have problem here. How's look the glue? Can you post a picture here to see your set up?
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Currently I don't have a picture maybe next week I can get one. The problem remains getting to high speeds to generate high pressure with the TD04, we are forced to get in the range of 110-120000 rpm. For direct-drive we need a TP4040-SCM but we cannot trust at this speed a manufacturer and the precision of assembly is crucial. Perhaps our project is too ambitious for the small budget and volumetric compressors provide more feasibility and reliability.
 
I think you had enough precision in your assembly. The bearing should not fail with a rotational force.
Sure you need a lot RPM and thats the difficult part. Maybe you should get an other compressor? There's a lot of chinese compressor for cheap. I currently have a chinese GT35 and I paid 80$ for it so it's not too bad to change compressor. I think you should find a compressor that have a smaller RPM or gear it and hope for your motor to have enough torq
 
WB projects said:
I think you had enough precision in your assembly. The bearing should not fail with a rotational force.
Sure you need a lot RPM and thats the difficult part. Maybe you should get an other compressor? There's a lot of chinese compressor for cheap. I currently have a chinese GT35 and I paid 80$ for it so it's not too bad to change compressor. I think you should find a compressor that have a smaller RPM or gear it and hope for your motor to have enough torq
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The problem with big impeller is the low volume flow of our engine due the low displacement. I think that surge appear and can destroy the impeller or limit the sistem reliability.
 
WB projects said:
I understand I have the same issue! I'm on the limite of airflow for my engine and I had surge at low rpm in the past
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AlexLTDLX said:
The bearings in my TP Power motor aren't rated for the speeds the motor can turn. I wonder if that's an issue here? WB could be right - it could also be surge beating things up.
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Do you know any manufacturers that have all the mechanical accommodations to achieve high speeds?

LMT has very high prices but if it is worth it we can try.
 
The next motor I will try is the castle 1721. It's the fastest/strongest motor I know of. I need it because I have direct drive set up and I need arround 70k rpm. This motor is rated at 90k rpm (no load).
I don't think it's possible to find a 120k rpm motor in load. If you really want to go to this RPM, sure you can gear it! But with the problems alex had in the past, you need to find a motor that will be able to run slower but stronger. Brushless motor like to be efficient and run in there "max" RPM
 
After looking at the data, the LMT motors seem to do very well (efficiency-wise) under heavy load and high rpm. The 1950 can do 85k rpms, and then if you add the carbon sleeve, 30% higher (110.5k rpm). I don’t know how much power is needed though.
 
Here is the 6 turn (delta terminated Im assuming) continous duty
 

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